Colored granular detergent products are well known. Also well known are distinctively colored granular detergent products containing dyes or pigments which have a beneficial "bluing" effect on fabrics resulting in an improvement of apparent fabric whiteness. U.S. Pat. No. 2,930,760 issued Mar. 29, 1960 describes the use of the water-soluble dye, Polar Brilliant Blue GAW (similar to C.I. 61135), as an effective non-staining bluing agent in a detergent product. U.S. Pat. No. 3,529,923 issued Sept. 22, 1970, describes a bluing composition containing the water-insoluble pigment Ultramarine Blue (C.I. 77007) which has a greatly reduced potential for staining fabrics.
The preparation of colored granular detergent products is generally accomplished by mixing a coloring material into a detergent composition prior to spray drying it into granules. Alternatively, coloring materials can be present in only a portion of the granules in the total detergent product to provide a speckled appearance. These speckles can be prepared by spray drying. They can also be prepared by an agglomeration method, such as described in U.S. Pat. No. 3,035,30l issued May 22, 1962, which utilizes water solutions of adhesives to agglomerate hydratable salts. A coloring material can be present in the adhesive solution to provide a colored speckle. Still another alternative is provided by U.S. Pat. No. 2,889,283 issued Apr. 29, 1956 which describes a process for spraying a water solution or suspension of a coloring material onto a diverted portion of a granular detergent composition process stream. A speckled appearance results by blending the undiverted and uncolored stream with the stream subjected to the spray containing a coloring material.
All these methods provide a distinctly visible color to the finished granular detergent product. definite
In order to meet the requirements of some users of granular detergent products and to minimize fabric staining due to localized high concentrations of coloring material, it is desirable to provide a granular detergent product that is substantially uncolored in its dry state yet contains sufficient coloring material to provide a definiate color to a washing solution. Additionally, depending on the coloring material used, it is desirable to provide a benefit to fabrics washed in such solutions.
Canadian Pat. No. 586,019 issued Oct. 27, 1959 describes a granular detergent composition in which a coloring material is distributed in a dry state and in a state of subdivision such that the dry composition is not appreciably colored. The process by which these compositions are prepared does not result in agglomeration or adhesion of the coloring material to prevent subsequent separation from the bulk of the composition.
It is an object of the present invention to provide a granular detergent product substantially uncolored in its dry state which contains coloring materials that are not subject to separation and segregation and are readily soluble or dispersible when the granular detergent product is mixed with water to form a washing solution.